As an encoding scheme for compression recording of moving images, H.264/MPEG-4 AVC (hereinafter, referred to as H.264) is known (NPL 1: ITU-T H.264 (June 2011) Advanced video coding for generic audiovisual services). In H.264, a plurality of profiles that define limits in encoding technology are defined. For example, High 10 profile corresponds to an image of a bit depth ranging from 8 bits to 10 bits.
In recent years, activities to achieve international standardization of an encoding scheme with higher efficiency as a successor of the H.264 have been launched. Between the International Organization for Standardization (ISO)/the International Electrotechnical Commission (IEC) and the International Telecommunication Union Telecommunication Standardization Sector (ITU-T), Joint Collaborative Team on Video Coding (JCT-VC) has been established. In the JCT-VC, standardization of a high efficiency video coding (HEVC) encoding scheme (hereinafter, abbreviated as HEVC) is underway.
A Main 10 profile, which corresponds to an image of a bit depth ranging from 8 bits to 10 bits, is defined also in HEVC (NPL2: JCT-VC contributions JCTVC-K1003_v10.doc Internet <http://phenix.int-evry.fr/jct/doc_end_user/documents/11_Shanghai/wg11/>).
In HEVC, in processing of orthogonal transform, motion compensation, or the like, by reducing the arithmetic precision in accordance with the bit depth of an image, an emphasis is placed on the easiness of implementation. For example, expression (1) provided below is one of calculation expressions used for motion compensation processing on a decimal pixel, in motion compensation for chrominance signals.[Math.1]ab0,0=(−2×B−1,0+58×B0,0+10×B1,0−2×B2,0)>>shift1  (1)
It should be noted that in expression (1), “shift1” represents the chrominance bit depth minus 8 and “>>” represents bit shift to the right.
In expression (1), “Bi,j” represents intermediate values for calculating a chrominance pixel at an integer pixel position and “ab0,0” represents a chrominance pixel at a decimal pixel position, respectively. Expression (1) includes bit shift processing to the right by “shift1” which is always dependent on the bit depth. Therefore, the range of a value which the intermediate value “ab0,0” may take is constant, regardless of the bit depth of an image. Since such arithmetic processing is introduced, it is considered that in HEVC, implementation cost of the hardware does not increase so much even when an image of higher bit depth is supported. On the contrary, through an arithmetic operation typified by the bit shift processing described above, arithmetic precision is reduced in the case of images of high bit depth. Therefore, there is a problem that the image quality does not improve.